his close associates Qi Tai and Huang Zicheng, made plans to demand the reduction of the military power of these perceived rivals. The first to be considered was Zhu Yuanzhang's fourth son Zhu Di, Prince of Yan, since he had the largest territory, but the proposal was declined. Soon after, in July 1398, the Jianwen Emperor arrested his fifth uncle Zhu Su, Prince of Zhou in Kaifeng, on treason charges. The prince and his family members were stripped of royal status and exiled to Yunnan. In April 1399, three more of Zhu Yuanzhang's sons, the princes of Qi, Dai, and Xiang, and their family members were stripped of their royal status. The princes of Qi and Dai were placed under house arrest in Nanjing and Datong, respectively, while the Prince of Xiang committed suicide. Two months later another son, the Prince of Min, also lost his royal status and was exiled to Fujian. As the rift between the regional princes and their emperor nephew grew, the Prince of Yan, who was the eldest surviving uncle of the emperor, and commanded the most powerful military, effectively assumed the leadership role among the uncles. Initial stage, 1399 Attack on Beiping In December 1398, to prevent what he believed was a potential attack from his uncle, the Prince of Yan, the Jianwen Emperor had appointed several imperial staff to Beiping (present day Beijing) where Zhu Di was stationed. In response, Zhu Di pretended to be ill while preparing for the anticipated war. However, the conspiracy was reported to the imperial staff in Beiping by one of the staff in Yan court. As a result, the arrest for the Prince of Yan was ordered by the imperial court. Zhang Xin, one of the imperial staff, decided to leak the imperial order to the Prince of Yan. To prepare for the imminent arrest, Zhu Di ordered his general Zhang Yu to gather 800 men to patrol the Yan residence in Beiping. In July, the imperial staff surrounded the Yan residence, and Zhu Di responded by executing the imperial staff and then storming the gates of Beiping. By nightfall, Zhu Di was in control of the city and had officially rebelled against the imperial court. For the next several days, the Yan forces captured Tongzhou, Jizhou, Dunhua and Miyun. By the end of July, Juyong Pass, Huailai and Yongping all fell to the Yan forces and